Independent self adjusting vibration damper

ABSTRACT

The torque-transmitting connections between a turbine rotor and the individual turbine blades include centrifugally responsive vibration damping elements having limited freedom to swing an individual coupling shafts between plates securing each blade to the rotor assembly. The torque transfer value varies as the speed varies, to damp vibrations due to speed fluctuations.

United States Patent 1 Crick 1 Mar. 27, 1973 [541 INDEPENDENT SELFADJUSTING VIBRATION DAMPER [75] Inventor: Virlon Crick, Southwick, Mass.

[73] Assignee: The United States of America as represented by theSecretary of the Air Force [22] Filed: May 5, 1971 [21] Appl. N0.:140,401

[52] 11.8. C1 ..416/219, 416/500 [51] Int. Cl ..F01d 5/16 [58] Field ofSearch ..4l6/2l4, 500, 220, 219, 221

[56] References Cited 7 UNITED STATES PATENTS 3,266,770 8/1966 Harlow..416/l90 X FOREIGN PATENTS OR APPLICATIONS France ..416/500 1,223,3151/1960 France ..4l6/50O 1,263,677 5/l96l France ..4l6/500 561,754 4/1957Italy ..4l6/5OO Primary Examiner-Everette A. Powell, Jr. Attorneyl-IarryA. Herbert, Jr. and Henry S. Miller, Jr.

[57] ABSTRACT The torque-transmitting connections between a turbinerotor and the individual turbine blades include centrifugally responsivevibration damping elements having limited freedom to swing an individualcoupling shafts between plates securing each blade to the rotorassembly. The torque transfer value varies as the speed varies, to dampvibrations due to speed fluctuations.

1 Claim, 2 Drawing Figures PATENTEDMARZYISB 7 3,023

:FIEZ

V I R N INVENTOR.

C l K ATTORNEYS INDEPENDENT SELF ADJUSTING VIBRATION DAMPER BACKGROUNDOF THE INVENTION This invention relates generally to a means forvibration-damping in axial-flow turbomachines and more specifically to ameans that is responsive to centrifugal force for minimizing thevibration in turbine blades.

Before this invention, the so called toggle" dampers for turbine bladeswere assembled by attachment to the rear blade retaining plate. Eachtoggle'damper contacted two adjacent turbine blades at the rear bladeplatform. This design incorporates certain inherent disadvantages. Onedisadvantage is damper loading at the rear platform rather than the moredesirable uniform damper loads fore and aft along the blade mounting.Another disadvantage in prior art design was an excessive leakage of aircaused by toggle dampers being mounted from the rear retaining plate.This invention overcomes the disadvantages of known toggle" dampers.

SUMMARY OF THE INVENTION The invention consists of a pair of vibrationdampers each being generally rectilinear at one end and bifurcated atthe other. Each of the pair of vibration dampers are secured to the endof a shaft by an interference fit. The resulting damper assembly is acomplete unit, independent of other engine parts or components.

During assembly of the turbine rotor, the damper assembly is trappedfore and aft by blade retaining plates. It is further trapped radiallyoutward by the turbine blade and radially inwardly by the turbine disk.The damper assembly per se is not attached to any of the aforementionedcomponents, rather it is confined to an area defined by these parts.

It is therefore an object of the invention to provide a new and improvedturbine blade vibration damper.

It is another object of the invention to provide a new and improvedvibration damper for turbine blades that is self adjusting.

It is a further object of the invention to provide a new and improvedvibration damper that provides a uniform damper load on the turbineblade.

It is still another object of the invention to provide a new andimproved vibration damper that minimizes air leakage from the turbine.

It is still a further object of the invention to provide a new andimproved vibration damper that is an indepen dent part of the turbinerotor-blade assembly.

These and other advantages, features and objects of the invention willbecome more apparent-from the following description taken in connectionwith the illustrative embodiments in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of thevibration damper assembly installed on a turbine disk.

FIG. 2 is an elevational view of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. 1, thevibration dampers l0 and 12 are secured to a shaft 14 by an interferencefit at 16 and 18. The vibration dampers are constructed partialpbifurcated at one end and having a pair of contact sur aces 7 and 9WhlCl'l are designed to contact the blade platforms 11 and 13.

At assembly of the high pressure turbine rotor, the

damper assembly (10, 12 and 14) is trapped fore and aft of the rotorslongitudinal axis by the blade retaining plates 20 and 22. The turbineblade consists of a vane 23,platform 24 and shank 25 and is secured tothe rotor disk by a conventional dove tail slot means between the shankand disk. Radially outward, the turbine blade base 24 confines thedamper assembly and radially inward it is restrained by the turbine disk26.

The described area at the base of each turbine blade contains the damperassembly which is a complete unit, independent of other engine parts.FIG. 2 shows that in operation, as the turbine begins to rotate, thedamper assembly 30 is loaded against the blade platforms 32 33 and 35 ofthe blades 37 and 39 by centrifugal force. Since the damper assembly isself-adjusting the assembly will adjust itself to the vibration of theblade and dampen the blade motion accordingly. For example, if thedamper assembly contacts the blade platforms as shown in FIG. 2 atpoints 34, 36 and 38, the centrifugal force would create a moment aboutpoint 38 which would overcome the resistance to turning created by theinterference fit and move the assembly unit point 40 contacts the bladeplatform.

With the adjustment accomplished, friction dampening will then occur atboth front and rear dampers by the relative motion of the blades withrespect to the dampers.

Having thus described my invention for an independent, self-adjustingvibration damper for turbine blades, the following are my claims ofinvention.

Iclaim:

1. A self adjusting vibration dampering system for turbine bladescomprising: a shaft; a first and second damper assembly mounted atopposite ends of said

1. A self adjusting vibration dampering system for turbine bladescomprising: a shaft; a first and second damper assembly mounted atopposite ends of said shaft and having an interference fit therewith,said assemblies being rectangular on one end and having a plurality ofcontact surfaces on the opposite end and adapted to contact the base ofadjacent turbine blades upon movement of the turbine rotor disk.